A study of collagen structure and collagen turnover with special emphasis on the specificity of hydroxylation of proline residues to form 3- and 4-hydroxyproline in various collagens. The substrate specificity of the prolyl hydroxylase of earthworm subcuticular epithelium, and of rat skin will be studied. The synthesis, metabolism and excretion of 3-hydroxyproline will be studied, in relation to basement membrane turnover. The peptides in which 3-hydroxyproline is excreted will be studied with respect to their diversity, metabolism, and probable source in the various collagen types. The properties and stability of synthetic collagen-like polytripeptides, containing 3- or 4-hydroxyproline in specific sequence positions will be studied.